1. Field of the Invention
The present invention relates to a reciprocating piston type refrigerant compressor adapted for being used in an airconditioning system of an automobile, and more particularly, it relates to a multi-piston swash plate type refrigerant compressor provided with a housing in which damping of discharge gas pulsation is achieved and with a simple construction of the compressor in which separate parts are not needed for sealing a discharge passageway.
2. Description of the Related Art
For aiding in understanding of the present invention, reference is made firstly to FIGS. 1, 2 and 3 showing a conventional reciprocating piston type refrigerant compressor. FIG. 1 is a longitudinal cross-sectional view, and FIGS. 2 and 3 show front and rear housings, respectively. The compressor is provided with front and rear cylinder blocks 1 and 1a which are axially connected to one another so as to form an integral cylinder block assembly. Front and rear ends of the cylinder block assembly are closed by front and rear housings 8 and 9, via front and rear valve plates 10 and 11. The front and rear cylinder blocks 1 and 1a, front and rear valve plates 10 and 11 and front and rear housings 8 and 9 are tightly held by through-bolt(not shown) which are inserted into coaxial through-bores 12 and 12a. The combined cylinder blocks 1 and 1a are further provided with an axial central bore including coaxial front and rear bores 7 and 7a formed in the front and rear cylinder blocks 1 and 1a, respectively. The central bore supports an drive shaft 14, via metal bearings 7b and 7c. Lubrication oil is provided with the cylinder blocks 1 and 1a through oil supplying passageway 13 and 13a.
A plurality of cylinder bores 2, the same number of front and rear cylinder bores, are formed around a longitudinal axis of the combined cylinder blocks 1 and 1a. Double-headed pistons 4 are received in the cylinder bores 2 and engage a with a swash plate 3 via semi-circular shoes 6.
The cylinder block assembly has a swash plate chamber 5 formed therein at the juncture of the cylinder blocks 1 and 1a, and the swash plate 3 is arranged in the swash plate chamber 5 and mounted on the drive shaft 14. The swash plate 3 is rotated together with the drive shaft 14 which in turn is rotated according to rotation of an electromagnetic clutch 14a, and therefore the double-headed pistons 4 are reciprocated in the cylinder bores 2.
The front and rear housings 8 and 9 are provided with inner front and rear discharge chambers 16 and 17, and radially outer front and rear suction chambers 23 and 24 formed therein, respectively. The front and rear valve plates 10 and 11 have suction ports 27 and 28 bored therein, respectively, so as to provide fluid communication between the suction chambers 23 and 24 and the respective cylinder bores 2. The front and rear valve plates 10 and 11 also have discharge ports 21 and 22 bored therein, respectively, so as to provide fluid communication between the discharge chambers 16 and 17 and the respective cylinder bores 2.
The suction ports 27 and 28 are closed by front and rear suction valves 25 and 26 in the form of reed-valves arranged to make contact with inner faces of the front and rear valve plates 10 and 11. Similarly, the discharge ports 21 and 22 are closed by front and rear discharge valves 19 and 20 in the form of reed-valves arranged to make contact with the outer faces of the front and rear valve plates 10 and 11. The suction and discharge valves 25, 26, 19, and 20 can be moved away from the corresponding suction and discharge ports 27, 28, 21, and 22 by the compression stroke of the double-headed pistons 4 so as to open the respective suction and discharge ports.
Certain clearances 15 and 15a are formed between the outer peripheral wall of the combined cylinder blocks 1 and 1a and the inner peripheral wall of the front and rear housings 8 and 9 assembled, and communication holes (not shown) are formed in the cylinder blocks 1 and 1a in order to provide fluid communication between the swash plate chamber 5 and the clearances 15 and 15a. The refrigerant gas is introduced into an inlet chamber 43 (FIG. 3) through a refrigerant inlet port (not shown) from the external airconditioning system, and then is delivered into the swash plate chamber 5 through openings (not shown) and the communication holes formed in the cylinder blocks 1 and 1a, the openings being formed in a valve assembly including the valve plate 11 and the suction and discharge valves 26 and 20. The refrigerant gas introduced into the swash plate chamber 5 flows into the suction chambers 23 and 24 via suction passageways axially formed in the cylinder blocks 1 and 1a. Then, the refrigerant gas passes into the respective cylinder bores 2 due to the suction operation of the respective double-headed pistons 4. The refrigerant gas in the respective cylinder bores 2 is discharged from the cylinder bores 2 into the discharge chambers 16 and 17. The compressed refrigerant gas flowing into the discharge chamber 16 in the front housing 8 is carried into the discharge room 41 in the rear housing 9, via an extended discharge port 40 and discharge passageways 39 and 39a coaxially formed in the cylinder blocks 1 and 1a. The refrigerant gas into the discharge room 41 and the refrigerant gas coming from the discharge chamber 17 in the rear housing 9 through a discharge passageway 37 are collected in the discharge room 41. Then, the compressed refrigerant gas is delivered toward the external airconditioning system through an outlet port 42 of the compressor.
An O-ring 29 is provided to prevent leakage of the refrigerant gas from the junction of the combined front and rear housings 8 and 9, and mounting lugs 32 are provided for mounting the compressor to the framework of an automobile chasis.
As depicted in FIGS. 2 and 3, in the front and rear housings 8 and 9, axial bores 34 and 34a and a plurality of walls 35 and 36 extending from bosses 34b and 34c are formed, respectively, so as to provide support for the valve assembly. An inner wall 35a of the front housing 8 divides the front suction and discharge chambers 23 and 16, and the rear suction and discharge chambers 24 and 17 are formed in the rear housing 9 by an inner wall 36a and an outer wall 36b. Between the inner and outer walls 36a and 36b of the rear housing 9, a discharge passageway 37 is provided. A communication path 38 in the rear housing 9 provides fluid communication between the discharge chamber 17 and the discharge passageway 37. Therefore, the refrigerant gas discharged into the discharge chamber 17 of the rear housing 9 is delivered toward the external airconditioning system through the outlet port 42 formed at the discharge room 41, via the communication path 38 and the discharge passageway 37. Also, the compressed refrigerant gas discharged into the discharge chamber 16 of the front housing 8 is carried into the discharge room 41 of the rear housing 9 via the extended discharge port 40 and the discharge passageways 39 and 39a, and then delivered toward the external airconditioning system through the outlet port 42.
With the above described swash plate type compressor, since the discharge passageway 37 to discharge the compressed refrigerant gas of the rear housing 9 toward the external airconditioning system is formed outside the discharge chamber 17 along the inner wall 36 of the discharge chamber 17, that is, formed extending with a certain length between the discharge chamber 17 and the suction chamber 24, difficulty has been met in closing the discharge passageway 37 by anti-leaking means such as a gasket. Namely, the upper opening of the discharge passageway 37 must be closed by the separate gasket, because the upper opening is not covered by the rear valve plate 11 and the rear suction and discharge valves 26 and 20. This requires complexity in construction of the compressor. The narrow and long semicircular structure of the discharge passageway 37 becomes obstacle in refrigerant flow, and eventually creates pressure loss.
Further, the discharge passageway 37 occupies a certain area of the suction chamber 24 so as to reduce the volume of the suction chamber 24. The outer wall 36b, which defines boundary between the suction chamber 24 and the discharge passageway 37, covers partially the suction ports which are placed above the suction passageway 37 among the suction ports of the valve plate 11, and accordingly, the suction operation of the refrigerant gas between the swash plate chamber 5 and the suction chamber 24 of the rear housing 9 is subject to a large resistance.
Moreover, where any design modifications on the structure of the discharge passageway 37 occur to improve it, the parts such as a gasket relating to the discharge passageway 37 must also be changed, and this is not desirable from the viewpoint of costs.